1. Field of the Invention
The present invention relates to a plasma processing apparatus such as a plasma chemical vapor deposition apparatus and a plasma etching apparatus, which are used for manufacturing semiconductor devices such as various kinds of sensors using semiconductor materials, thin film transistors, solar batteries and others, and for these purposes, are operable to form a film on a substrate or effect etching on a deposited film in accordance with a predetermined pattern, for example, for forming a wiring pattern.
In the specification and the appended claims, the plasma chemical vapor deposition is referred to also as "plasma-CVD".
2. Description of the Background Art
Various types of plasma-CVD apparatuses have been known.
As a typical example, a parallel plated plasma-CVD apparatus will be described below with reference to FIG. 9. This apparatus has a process chamber 1, in which electrodes 2 and 3 opposed to each other are arranged. The electrode 2 also serves as a substrate holder for mounting a substrate S1 to be processed thereon.
The electrode 2 is generally a ground electrode, and is provided with a heater 21 for heating the substrate S1 mounted on the electrode 2 to a deposition temperature. If radiated heat is used to heat the substrate S1, the heater 21 is separated from the electrode 2.
The electrode 3 is a power application electrode for applying a radio-frequency power or a direct-current power to the deposition gas introduced between the electrodes 2 and 3 for forming plasma from the gas. In this illustrated example, the electrode 3 is connected to a radio-frequency power source 32 via a matching box 31, and is electrically isolated from the process chamber 1.
In the illustrated embodiment, the electrode 3 includes as its component a gas nozzle 33 and a perforated electrode plate 34 provided at the opening of the nozzle 33. The perforated electrode plate 34 is provided with a large number of gas supply ports of about 0.5 mm in diameter, through which a gas supplied from the gas nozzle 33 is discharged entirely into a space between the opposed electrodes. This structure is suitable for deposition of a film on a large area of the substrate.
In the specification and the appended claims, "radio-frequency" may be referred to as "rf", and "radio-frequency power" may be referred to as "rf-power".
The process chamber 1 is also connected to an exhaust pump 52 via a valve 51, and the gas nozzle 33 is connected to a gas supply 4 via a piping. The gas supply 4 includes one or more gas sources 441, 442, . . . for supplying a deposition gas via one or more mass-flow controllers 421, 422, . . . and valves 431, 432, . . . , respectively.
According to the above parallel plated plasma-CVD apparatus, the substrate S1 for deposition is mounted on the electrode 2 in the process chamber 1. The process chamber 1 is maintained at a predetermined vacuum pressure by opening the valve 51 and driving the exhaust pump 52, and the deposition gas is introduced into the chamber 1 from the gas supply 4 through the nozzle 33 and the gas supply ports in the electrode plate 34. The power supply 32 applies an rf-power to the rf-electrode 3 to form plasma from the introduced gas, and an intended film is deposited on the surface of the substrate S1 in the plasma.
Various types of plasma etching apparatuses are also known.
As a typical example, a parallel-plated etching apparatus will be described below with reference to FIG. 10. This apparatus includes a process chamber 10, in which electrodes 20 and 30 opposed to each other are arranged. The electrode 20 serves also as a substrate holder for mounting a substrate S2 on which a film to be etched is formed.
The electrode 20 serves as a power application electrode for applying an rf-power or a DC power to an etching gas introduced between the electrodes 20 and 30 so as to form plasma. In the illustrated example, the electrode 20 is connected to an rf-power supply 202 via a matching box 201, and is electrically isolated from the process chamber 10.
The electrode 30 is a ground electrode, and includes as its component a gas nozzle 301 and a perforated electrode plate 302 provided at the opening of the nozzle 301. The perforated electrode plate 302 is provided with a large number of gas supply ports of about 0.5 mm in diameter, through which a gas supplied from the gas nozzle 301 is discharged entirely into a space between the opposed electrodes.
The process chamber 10 is also connected to an exhaust pump 72 via a valve 71, and the gas nozzle 301 is connected to a gas supply 6 via a piping. The gas supply 6 includes one or more gas sources 641, 642, . . . for supplying a etching gas via one or more mass-flow controllers 621, 622, . . . and valves 631, 632, . . . , respectively.
According to the above etching apparatus, the substrate S2 to be processed is mounted on the rf-electrode 20 in the process chamber 10. The chamber 10 is maintained at a predetermined vacuum pressure owing by opening the valve 71 and driving the exhaust pump 72, and the etching gas is introduced into the chamber 10 from the gas supply 6 through the nozzle 301 and the gas supply ports in the electrode plate 302. The rf-power supply 202 applies an rf-power to the electrode 20 to form plasma from the introduced gas, and the film on the substrate S2 is etched in the plasma. The electrode 20 may be cooled with a water-cooling device 200 or the like, if necessary.
The plasma CVD-apparatus described above presents such problems that particles which become dust are generated by gas phase reaction in the plasma, and the particles adhere to or are mixed into the film formed on the surface of the substrate, resulting in deterioration of the film quality, and that the particles thus generated adhere to various portions in the process chamber, causing contamination. Since the particles once adhered to the various portions in the process chamber may be separated therefrom and adhere to the substrate to be processed, they must be cleaned off before separation, which requires a time-consuming operation.
In particular, generation of particles by the gas phase reaction and growth thereof are likely to occur especially in such cases that an amorphous silicon film is formed from monosilane (SiH.sub.4) and hydrogen (H.sub.2), an amorphous silicon nitride film is formed from monosilane and ammonia (NH.sub.3), and an amorphous silicon oxide film is formed from monosilane and nitrous oxide (N.sub.2 O). For example, if the particles adhering to or mixed into the film deposited on the substrate surface have a size relatively larger than a film thickness of the deposited film, portions of the film containing the particles will form pin holes when cleaned after the deposition, so that, if the film is to be used as an insulating film, failure in insulation properties occurs, and, if the film is to be used as a semiconductor film, semiconductor characteristics are impaired.
Likewise, the plasma etching apparatus presents such disadvantages that particles which become dust are formed by the gas phase reaction and adhere to the etching surface or portions in the process chamber.
For example, if etching is performed for forming an interconnection or wiring pattern, such particles deteriorate the patterning accuracy, and may break an extremely thin line or interconnection.
The above disadvantages may impede high-speed deposition and high-speed etching, which generate many particles, and the particles impede stable formation of the plasma, so that failure in deposition and etching may be caused.